Theoretical analysis of the adsorption of ammonia–borane and their dehydrogenation products on the (001) surface of TiC and ZrC

Abstract

© 2018 Elsevier B.V.The adsorption of ammonia–borane (AB) over the (001) surface of TiC and ZrC, has been studied systematically by means of periodic-boundary density functional calculations using slab models. We present evidence that a surface with an appreciable degree of polarity such as those used in this research, can simultaneously activate the N-H and B-H bonds of the AB molecule and its dimer AB-AB. The molecule is highly activated by both supports, and the N-H and B-H bonds are stretched long enough to release one or two hydrogens. Additionally, the bond distance B-N is shortened by 0.04 and 0.06 Å by TiC and ZrC supports respectively, which results in the strengthening of the bond, what seems convenient to avoid unwanted by-products (NH3, BH3, etc.). A systematic study for the adsorption of BH2NH2, which is isoelectronic with ethylene, was also done. The adsorption leads to a major elongation of the B-N bond with respect to the calculated value in the gas phase (0.17 and 0.18